DE102004054629A1 - Basic deactivators in POM production - Google Patents

Abstract

Process for preparation of polyoxymethylenes via polymerization of the monomers a) in the presence of cationic initiators b) and also, if appropriate, in the presence of regulators c), followed by deactivation and discharge from the reactor, which comprises using, as deactivator (d) at least one basic compound having at least 2 amino functions of different reactivity in one molecule.

Description

The The invention relates to an improved process for the production of Polyoxymethylenes.

It It is known that oxymethylene polymers by continuous bulk polymerization the monomers prepared in the presence of cationic initiators can be. This polymerization is common in Kneading or extruding or tubular reactors carried out. there can the temperature control be done so that the resulting oxymethylene polymer either in solid form (DE-A 1 161 421, DE-A 1 495 228, DE-A1 720 358, DE-A 3 018 898) or also obtained as a melt (DE-A 3 147 309). The workup of the in Solid form resulting polymer is known, see: DE-A 31 47 309, DE-A 36 28 561, EP-A 678 535, EP-A 699 965 and DE-A 44 23 617.

at the bulk polymerization are different process variants Prior art, including batch polymerization in trays, the continuous polymerization in kneader reactors at temperatures below the melting point or the polymerization at temperatures above the melting point of trioxane in the extruder (see WO 01/58974).

The Preparation by suspension or precipitation polymerization with cationic Initiators is generally known. In the solvent used here in particular, the resulting polymer should not be soluble, so that this is easier to separate.

Either in bulk and precipitation polymerization dissolution agents, so-called deactivators are added to the polymerization to end.

According to DE-A 36 17,754, DE-A 25 09 924, JP-A 59/197 415, WO 97/24384 and Res. Discl. Vol 190, page 61 (1980) basic compounds such as amines and inorganic / organic Bases of any kind are used.

The Deactivators known from the prior art cause problems in the work-up of the reaction mixture and, if appropriate, their Return in the polymerization. Usually, carriers or solvents are added to the very low needed To distribute amount of deactivators effectively in the polymer. The effectiveness The deactivation is crucial for the stabilization of the polymer and lets in the known deactivators still to be desired.

• – die kationischen Ladungen am Polymer werden stabilisiert und damit weitere Reaktionen im Polymer unterbunden,
• – diese sollen mit Formiatendgruppen reagieren können und damit instabile Endgruppen des Polymers binden,
• – als Formaldehydfänger und Radikalfänger dienen können,
• – durch die multiplen Reaktionsmöglichkeiten sollte dieses Agenz vorwiegend polymergebunden vorliegen. In diesem Fall ergeben sich Vorteile bei der Aufarbeitung des Polymers, da z.B. keine flüchtigen organischen Monomere (i.e. nichtumgesetzte Base) abgetrennt werden müssten.

The object of the present invention was therefore to provide an improved process for the preparation of polyoxymethylene which has the following advantages over the prior art:

• The cationic charges on the polymer are stabilized, thus preventing further reactions in the polymer,
• They should be able to react with formate end groups and thus bind unstable end groups of the polymer,
• - can serve as a formaldehyde scavenger and radical scavenger,
• - Due to the multiple reaction possibilities, this agent should be present predominantly polymer bound. In this case, there are advantages in the workup of the polymer, since, for example, no volatile organic monomers (ie unreacted base) would have to be separated.

Accordingly, became a process for the preparation of polyoxymethylenes by polymerization of the monomers a) in the presence of cationic initiators b) and optionally in the presence of regulators c) and subsequent deactivation as well as discharge from the reactor found, which characterized is that as deactivator d) at least one basic compound with at least 2 amino functions of different reactivity in one molecule starts.

preferred embodiments are the dependent claims refer to.

The Procedure can basically be carried out on any reactors with a high mixing effect, such as trays, plowshare mixers, tubular reactors, static Mixers, trickle reactors, kneaders, stirred reactors, extruders and Belt reactors.

The resulting POM polymers are known in the art per se and described in the literature.

In general, these polymers have at least 50 mole percent of recurring units -CH ₂ O- in the polymer backbone.

The Homopolymers are generally obtained by the polymerization of Monomers a) such as formaldehyde or trioxane prepared, preferably in the presence of suitable catalysts.

wobei R¹ bis R⁴ unabhängig voneinander ein Wasserstoffatom, eine C₁-bis C₄-Alkylgruppe oder eine halogensubstituierte Alkylgruppe mit 1 bis 4 C-Atomen und R⁵ eine – CH₂-, -CH₂O-, eine C₁- bis C₄-Alkyl- oder C₁- bis C₄-Haloalkyl substituierte Methylengruppe oder eine entsprechende Oxymethylengruppe darstellen und n einen Wert im Bereich von 0 bis 3 hat. Vorteilhafterweise können diese Gruppen Ringöffnung von cyclischen Ethern in die Copolymere eingeführt werden. Bevorzugte cyclische Ether sind solche der Formel

wobei R¹ bis R⁵ und n die oben genannte Bedeutung haben. Nur beispielsweise seien Ethylenoxid, 1,2-Propylenoxid, 1,2-Butylenoxid, 1,3-Butylenoxid, 1,3-Dioxan, 1,3-Dioxolan und 1,3-Dioxepan als cyclische Ether genannt sowie lineare Oligo- oder Polyformale wie Polydioxolan oder Polydioxepan als Comonomere genannt.In the context of the invention, preference is given to polyoxymethylene copolymers, in particular those which, in addition to the repeating units -CH ₂ O-, also contain up to 50, preferably from 0.01 to 20, in particular from 0.1 to 10, mol% and very particularly preferably from 0.5 to 3 mol% of recurring units.

where R ¹ to R ⁴ independently of one another are a hydrogen atom, a C _{1 to} C ₄ alkyl group or a halogen-substituted alkyl group having 1 to 4 C atoms and R ^{5 is} a - CH ₂ -, -CH ₂ O-, a C ₁ - to C ₄ alkyl or C ₁ - to C ₄ haloalkyl substituted methylene group or a corresponding oxymethylene group and n has a value in the range of 0 to 3. Advantageously, these ring opening groups of cyclic ethers can be introduced into the copolymers. Preferred cyclic ethers are those of the formula

wherein R ¹ to R ⁵ and n have the abovementioned meaning. For example, ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane and 1,3-dioxepane are mentioned as cyclic ethers and linear oligo- or polyformals such as polydioxolane or polydioxepan called comonomers.

und/oder

wobei Z eine chemische Bindung, -O-, -ORO- (R=C₁- bis C₈-Alkylen oder C₃- bis C₈-Cycloalkylen) ist, hergestellt werden.Also suitable are Oxymethylenterpolymerisate, for example, by reacting trioxane or one of the cyclic ethers described above with a third monomer, preferably bifunctional compounds of the formula

and or

wherein Z is a chemical bond, -O-, -ORO- (R = C ₁ - to C ₈ -alkylene or C ₃ - to C ₈ -cycloalkylene) can be prepared.

preferred Monomers of this type are ethylene diglycidyl, diglycidyl ether and diether from glycidylene and formaldehyde, dioxane or trioxane in the molar ratio 2: 1 and diether from 2 mol glycidyl compound and 1 mol of an aliphatic Diols with 2 to 8 carbon atoms such as the diglycidyl ethers of ethylene glycol, 1,4-butanediol, 1,3-butanediol, cyclobutane-1,3-diol, 1,2-propanediol and cyclohexane-1,4-diol, to name just a few examples to call.

End-group stabilized polyoxymethylene polymers which have C-C or -O-CH ₃ bonds at the chain ends are particularly preferred.

The preferred polyoxymethylene copolymers have melting points of at least 150 ° C and weight average molecular weights M _w in the range of 5,000 to 300,000, preferably 7,000 to 250,000.

Particular preference is given to POM copolymers having a nonuniformity (M _w / M _n ) of from 2 to 15, preferably from 3 to 12, particularly preferably from 3.5 to 8. The measurements are generally carried out by (GPC) SEC (size exclusion The M _n value (number average molecular weight) is generally determined by (GPC) SEC (size exclusion chromatography).

Especially preferred POM copolymers have a bimodal molecular weight distribution on, wherein the low molecular weight fraction has a molecular weight of 500 to 20,000, preferably from 1,000 to 15,000 and in area proportions from 1 to 15, preferably 5 to 10% in the distribution graph w (log M) is present against log M.

Prefers have the according to the inventive method available Raw polyoxymethylene one Residual formaldehyde content in accordance with VDA 275 in the granules of a maximum of 3%, preferably at most 1%, preferably maximum 0.05%.

The average particle size (d ₅₀ value) (particle size) of the POM polymers is preferably from 0.5 to 20 mm, preferably from 0.75 to 15 mm and in particular from 1 to 7 mm.

As a rule, a d ₅₀ value is understood to mean the particle size value at which 50% of the particles have a smaller particle size and 50% have a larger particle size. This is to be understood accordingly for the stated d ₁₀ and d ₉₀ values.

The d ₁₀ value is preferably less than 1 mm, in particular 0.75 mm and very particularly preferably less than 0.5 mm.

Preferred d ₉₀ values are less than 30 mm and in particular less than 20 mm and very particularly preferably less than 10 mm.

Determination of the particle size distribution:

The particle size distribution was divided into different sieve fractions using a standard sieve set (analytical sieves according to DIN 4188) and these were weighed out. For example, d ₅₀ = 1 mm means that 50% by weight of the sample has a particle size less than or equal to 1 mm.

The inventive method is preferred for the homo- and copolymerization of trioxane applied. As a monomer a) but in principle any monomer described above, for example Tetroxane or (para) formaldehyde can be used.

The Monomers, for example trioxane, are preferably in the molten state Condition added, generally at temperatures of 60 to 120 ° C.

Preferably is the temperature of the reaction mixture at the dosage 62 to 114 ° C, in particular 70 to 90 ° C.

The If appropriate, molecular weights of the polymer can be determined by usual in the (trioxane) polymerization Controller c) can be set to the desired values. As a regulator c) come acetals or formals of monohydric alcohols, the alcohols themselves as well as those acting as chain transferers small amounts of water whose presence usually never Completely avoid, in question. The regulators are used in quantities of 10 to 10,000 ppm, preferably from 100 to 1,000 ppm.

When Initiators b) (also called catalysts) are the in the (trioxane) polymerization usual cationic starter used. Proton acids are suitable, such as fluorinated or chlorinated alkyl and arylsulfonic acids, e.g. perchloric acid, trifluoromethanesulfonic or Lewis acids, such as. Tin tetrachloride, arsenic pentafluoride, phosphoric pentafluoride and boron trifluoride and their complex compounds and salt-like Compounds, e.g. Boron trifluoride etherates and triphenylmethylene hexafluorophosphate. The catalysts (initiators) are used in amounts of about 0.001 to 1,000 ppm, preferably 0.01 to 100 ppm and in particular of 0.05 to 10 ppm used. In general, it is recommended that the Catalyst in dilute Add form, preferably in concentrations of 0.005 to 5 Wt .-%. As a solvent therefor can inert compounds such as aliphatic, cycloaliphatic hydrocarbons e.g. Cyclohexane, halogenated aliphatic hydrocarbons, glycol ethers etc. are used. Particularly preferred is triglyme as a solvent (Triethylene glycol dimethyl ether) and 1,4-dioxane.

monomers a), initiators b), and optionally regulator c) can any way premixed or separated from each other the polymerization reactor be added. Furthermore, can the components a), b) and / or c) for stabilizing steric hindered phenols contain as in EP-A 129369 or EP-A 128739 described.

For greater flexibility in the desired M _{w of} the POM polymer, it has proven to be advantageous to dissolve the regulator c) in small amounts of solvent and then to mix and meter with the monomers or comonomers.

In a preferred embodiment the polymerization is as a precipitation polymerization (depending on the degree of solubility the individual components can also be labeled as suspension polymerization) in a solvent carried out, in which the resulting polyoxymethylene homo- or copolymer largely insoluble is. Under "largely" insoluble be understood that from a degree of polymerization of at least 4, the polymer precipitates.

When solvent in particular inert compounds are used, for example aliphatic hydrocarbons such as propane, butane, pentane, iso-octane, n-hexanes, n-heptane, n-octane, isooctane and cycloaliphatic hydrocarbons such as cyclohexane or cycloheptane, as well as cyclopentane, which optionally Can carry heteroatoms as substituents.

When aromatic hydrocarbons are those which are suitable at least 6 to 30 carbon atoms, with nitrobenzene, toluene, benzene preferred are.

When further suitable halogenated hydrocarbons are dichloromethane, Chloroform, dichloroethane and trichloroethane.

Further are ethers such as dioxane or THF and triglyme (triethylene glycol dimethyl ether) as inert solvent suitable.

The solvent preferably has temperatures at the beginning of the reaction (metered addition) from 50 to 250 ° C preferably 55 to 180 and in particular 60 to 130 ° C on.

Preferably, before the beginning of the reaction under inert gas conditions, preferably under N ₂ , worked, at pressures of 1 to 5, preferably from 1 to 2 bar abs.

The Residence time for the polymerization in the solvent (Precipitation) is preferably 0.1 to 240 minutes, in particular 5 to 120 minutes. The polymerization is preferably up to a conversion of at least 30%, in particular more than 60% led. Under cheap Conditions can also be sales from 90% and above achieve quantitative sales up to 100% are well reproducible.

in the Generally, a driving has proven to be a pressure at the starting phase of the polymerization from 1 bar abs to 10 bar abs, preferably 2 bar abs to 7 bar abs sets. The polymerization preferably takes place under inert gas, preferably nitrogen.

In a further preferred embodiment the polymerization is carried out in water or a melt, such as these are described, for example, in EP-A 0 080 656 and EP-A 0 638 599 becomes.

Preferably will be followed directly the polymerization mixture deactivates the polymerization mixture, preferably without a phase change takes place.

• a) durch direkte Zugabe in die Polymerisationsvorrichtung, vorzugsweise Kessel(kaskade), zum ausgefällten POM (in Teilchenform), oder
• b) nach vollständiger Abtrennung des POM-Polymeren vom Lösungsmittel und anschließender Begasung mit gasförmigen Desaktivatoren, oder
• c) nach teilweiser Abtrennung des Lösungsmittels und Zugabe des Desaktivators in das verbleibende Lösungsmittel, welches das ausgefällte Polymer enthält, oder
• d) nach vollständiger Abtrennung des Polymeren vom Lösungsmittel und Auflösen des Polymeren in einem geeigneten Lösungsmittel sowie Zugabe des Desaktivators zum gelösten Polymeren.

The deactivation of the catalyst residues is generally carried out in the suspension polymerization by adding at least one deactivator d):

• a) by direct addition into the polymerization apparatus, preferably kettle (cascade), to the precipitated POM (in particulate form), or
• b) after complete separation of the POM polymer from the solvent and subsequent gassing with gaseous deactivators, or
• c) after partial removal of the solvent and addition of the deactivator in the remaining solvent containing the precipitated polymer, or
• d) after complete separation of the polymer from the solvent and dissolution of the polymer in a suitable solvent and addition of the deactivator to the dissolved polymer.

• a) durch Zugabe der reinen Substanz oder einer Lösung oder Suspension in die Reaktionsschmelze,
• b) durch Zugabe der Substanz, vorzugsweise per Seitenextruder oder Stopfschnecke in die Reaktionsschmelze.

In the preferred melt polymerization is usually the addition of the deactivator

• a) by adding the pure substance or a solution or suspension into the reaction melt,
• b) by adding the substance, preferably by side extruder or plug screw into the reaction melt.

Used according to the invention as deactivators (d) basic compounds with at least 2 amino functions of different reactivity in one molecule.

Under different reactivity For the purposes of the invention is meant a different basicity of the nitrogen and thus different affinity to the cationic center on the polyacetal. A different basicity is usually on one different molecular environment (see also Breitmaier / Jung, Organic Chemistry, Thieme Verlag 1978, p. 374 and 375 and Beyer / Walter, Textbook of Organic Chemistry, Hirzel Verlag Stuttgart 1998, p. 166).

Corresponding can Combinations of a primary and a secondary one or primary and tertiary or secondary and tertiary Amino functions or mixtures thereof are used. According to the invention these different amino functions are present in one molecule be, wherein the molecular weight preferably ≤ 400, in particular ≤ 200 gl mol is.

wobei R¹, R³, R⁴ und R⁵ unabhängig voneinander Wasserstoff oder eine C₁-C₁₀-Alkylgruppe und
R² Wasserstoff oder eine C₁-C₁₀-Alkylgruppe oder O-R⁵ bedeutet.Preferred compounds d) are those of the general formula I.

wherein R ¹ , R ³ , R ⁴ and R ^{5 are} independently hydrogen or a C ₁ -C ₁₀ alkyl group and
R ^{2 is} hydrogen or a C ₁ -C ₁₀ alkyl group or OR ⁵ .

Preferred radicals R ¹ to R ⁵ are independently hydrogen or a C ₁ -C ₄ alkyl group, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl.

Especially preferred deactivators d) are substituted N-containing heterocycles, in particular derivatives of piperidine, triacetonediamine (4-amino-2,2,6,6-tetramethylpiperidine) is particularly preferred.

The Amount is preferably from 0.001 to 500 ppm by weight, preferably from 0.05 to 100 and in particular from 0.5 to 10 wt ppm based on the total mass. The relationship d) to initiator b) is preferably 0.1: 1 to 50: 1, especially 0.5: 1 to 15: 1 and most especially 1: 1 to 10: 1; based on the molar amount of the initiator.

The Deactivators d) can also be mixed with known other demolition agents.

Then you can the resulting polymer with inert solvent, for example Acetone or cyclohexane are washed and with suitable devices of solvent separated, optionally cooled become.

By the driving style according to the invention receives a compact, powdery one Granules, whereby the emergence of coarse parts according to the state the technique is avoided.

at the melt polymerization is a polymer having in particular improved stability receive.

According to the procedure according to the invention gives Polyoxymethylenhomo- or copolymers, which contain 0.001 to 100 ppm by weight units derived from at least one basic compound d) with at least two amino functions of different reactivity, in particular those as listed above under the general formula I compounds , In particular, the chains have from 0.001 to 30, preferably from 0.01 to 10 and in particular from 0.1 to 2 and very particularly preferably from 0.1 to 1% of units which are derived from the deactivators d).

Prefers Such units are located at the polymer chain ends. Then you can the corresponding Polyoxymethylenpolymerisat with conventional Additives such as stabilizers, rubbers, fillers, etc. in usual Be further processed.

Examples

• All percentages are by weight

Examples 1-3

A Monomer mixture consisting of 94% trioxane, 6% dioxolane and 0.01 % Butylal was continuous at a flow rate of 1.5 l / h in a polymerization reactor (tubular reactor with static mixers, T = 175 ° C) dosed. 1 ppm of the initiator was dissolved as a solution (70% aqueous perchloric acid, 1% dissolved in triglyme) injected into the monomer stream, the reaction mixture was in a coiled tubing reactor with stat. Thoroughly mixed with mixers. After a polymerization of 4 m became an aqueous solution of the deactivator d) (see table) 1% in the polymer melt injected so that the terminator in twenty-fold excess amount to the initiator. After a residence time of about 3 min was the polymer melt discharged.

Subsequently was the thermal stability of the polymer in a TGA measurement (thermogravimetric analysis) determined, the sample at 5 ° C / min heated and the decrease in the sample weight was recorded (RT to 450 ° C).

• V = zum Vergleich

Mn / Mw was measured by GPC, standard: determined Ultraform ^® N 2320

• V = for comparison

Claims (10)

A process for the preparation of polyoxymethylenes by polymerization of the monomers a) in the presence of cationic initiators b) and optionally in the presence of regulators c) and subsequent deactivation and discharge from the reactor, characterized in that as deactivator (d) at least one basic compound at least 2 amino functions of different reactivity in a molecule. Method according to claim 1, characterized in that that as deactivator d) basic compounds having a primary and a secondary one or primary and tertiary or secondary and tertiary amino function or mixtures thereof. Process according to claims 1 or 2, characterized the molecular weight of the deactivator d) is ≦ 400 g / mol. Process according to claims 1 to 3, characterized in that compound d) of general formula I is used:

where R ¹ , R ³ , R ⁴ and R ⁵ independently of one another are hydrogen or a C ₁ -C ₁₀ -alkyl group and R ^{2 is} hydrogen or a C ₁ -C ₁₀ -alkyl group or OR ⁵ . Process according to claims 1 to 4, characterized in that one uses as deactivator d) compounds of general formula I, in which R ¹ , R ² , R ³ and R ⁴ independently of one another are hydrogen or methyl group. Process according to claims 1 to 5, characterized that 0.001 to 1000 ppm by weight of initiator b) is used. Process according to claims 1 to 6, characterized that 0.001 to 500 ppm by weight of deactivator d) is used. Process according to claims 1 to 4, characterized that the deactivator d) to initiator b) in the ratio 200: 1 to 0.1: 1. Polyoxymethylene homo- or copolymers obtainable according to the process claims 1 to 8, containing 0.001 to 100 ppm by weight of units which differ from at least one basic compound d) having at least 2 amino functions different reactivity in a molecule derived. Polyoxymethylene homo- or copolymers according to claim 9, in which 0.001 to 30% of the chains have units which derive from the deactivators d).